Refine your search
Collections
Co-Authors
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Sengupta, Sudipta
- History of Successive Deformations in Relation to Metamorphism-Migmatitic Events in the Schirmacher Hills, Queen Maud Land, East Antarctica
Abstract Views :168 |
PDF Views:4
Authors
Affiliations
1 Department of Geological Sciences, Jadavpur University, Calcutta 700032, IN
1 Department of Geological Sciences, Jadavpur University, Calcutta 700032, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 32, No 4 (1988), Pagination: 295-319Abstract
The basement complex in the Schirmacher Hills of East Antarctica records the impress of multiple episodes of metamorphism, migmatization and deformation. In the earliest event there was a regional metamorphism under granulite facies conditions and synkinematic migmatization leading to the development of charnockitic rocks. An amphibolite facies metamorphism was superimposed on them. This late event was closely associated with widespread granitization leading to the development of the majority of the quartzofeldspathic gneisses. In the earliest deformation, a migmatitic banding and a crude foliation formed in the charnockitic rocks. This was followed by a period of strong deformation during which two broadly coaxial sets of isoclinal folds (F2A and F2B) formed. The folding movement was also associated with widespread ductile shearing. The periods of amphibolite facies metamorphism, extensive granitization, F2 folding and the major phase of ductile shearing were overlapping. Localized pegmatite bodies were also emplaced during the later and much weaker folding movements of F3 and F4 and along some discordant ductile shear zones cutting across the axial surfaces of F2 folds.
- Subir Kumar Ghosh (1932-2008)
Abstract Views :208 |
PDF Views:140
Authors
Affiliations
1 Department of Geological Sciences, Jadavpur University, Kolkata, IN
1 Department of Geological Sciences, Jadavpur University, Kolkata, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 74, No 2 (2009), Pagination: 277-278Abstract
No Abstract.Full Text
- A Paradoxical Situation in Determining Relative Competence from Wavelength/Arclength Ratios Within Buckle Folded Multilayers
Abstract Views :209 |
PDF Views:1
Authors
Affiliations
1 Department of Geological Sciences, Jadavpur University, Kolkata-700 032, IN
1 Department of Geological Sciences, Jadavpur University, Kolkata-700 032, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 75, No Spl Iss 1 (2010), Pagination: 13-17Abstract
By measuring the ratio of wavelength to arclength of folds in closely associated disharmonically folded competent layers, it is possible to determine which layer has undergone a greater layer-parallel strain and has a smaller competence. This method may lead to a paradoxical situation. For example when foliated quartzite and mica schist layers are folded together, the mica schist laminae show a much larger buckle shortening than the quartzite layers. On the other hand, the geometry of folds in quartzite indicates that quartzite was more competent than the mica schist. The structure can be explained by different modes of buckling, general buckling in quartzite layers and internal buckling in strongly anisotropic mica schists.Keywords
Arc Length, Wavelength, Multilayer, Buckling, Internal Buckling.References
- BIOT, M.A. (1964) Theory of internal buckling of a confined multilayer structure. Geol. Soc. Amer. Bull., v.75, pp.563-568.
- BIOT, M.A. (1965a) Further development of theory of internal buckling of multilayers. Geol. Soc. Amer. Bull., v.76, pp.833-840.
- BIOT, M.A. (1965b) Mechanics of Incremental Deformations. John Wiley & Sobs, New York, London and Sydney.
- COBBOLD, P.R. (1976) Mechanical effect of anisotropy during large finite deformation. Bull. Soc. Geol. France, v.18, pp.1497-1510.
- COBBOLD, P.R., COSGROVE, J.W. and SUMMERS, J.M. (1971) Development of internal structures in deformed anisotropic rock. Tectonophysics, v.12, pp.155-178.
- GHOSH, S.K. (1968) Experiments on buckling of multilayers which permit inter-layer gliding. Tectonophysics, v.6, pp.207-249.
- HUDLESTON, P.J. (1986) Extracting information from folds in rocks. Jour. Geol. Educ., v.34, pp.237-245.
- HUDLESTON, P.J. (1973) An analysis of single layer folds developed experimentally in viscous medium. Tectonophysics, v.16, pp.189-214.
- RAMBERG, H. (1964) Selective buckling of composite layers with contrasted rheological properties, a theory for the formation of several orders of folds. Tectonophysics v.1, pp.307-341.
- RAMSAY, J.G. (1967) Folding and Fracturing of rocks. McGraw-Hill. New York.
- RAMSAY, J.G. and HUBER, M.I. (1987) The techniques of Modern Structural Geology, 2: Folds and fractures. Academic Press, London.
- SHERWIN, J. and CHAPPLE,W.M. (1968) Wavelength of single layer folds: a comparison between theory and observation. Amer. Jour. Sci., v.266, pp.167-179.